I like this and on all these dreadful quotes websites it's attributed to “Clara Ortega”. Searching the quote or the name just yields more dreadful quotes websites. Who is Clara Ortega??
There is mention of a Clara Ortega here http://en.wikipedia.org/wiki/Rancho_San_Ysidro but no indication at all if it is the same.
EDIT: I know it's not especially groundbreaking or elegant but if you have a sibling you feel that it is true about then it does make you smile.